Abstract
Inorganic cesium lead halide perovskites, as alternative light absorbers for organic–inorganic hybrid perovskite solar cells, have attracted more and more attention due to their superb thermal stability for photovoltaic applications. However, the humid air instability of CsPbI2Br perovskite solar cells (PSCs) hinders their further development. The optoelectronic properties of CsPbI2Br films are closely related to the quality of films, so preparing high-quality perovskite films is crucial for fabricating high-performance PSCs. For the first time, we demonstrate that the regulation of ambient temperature of the dry air in the glovebox is able to control the growth of CsPbI2Br crystals and further optimize the morphology of CsPbI2Br film. Through controlling the ambient air temperature assisted crystallization, high-quality CsPbI2Br films are obtained, with advantages such as larger crystalline grains, negligible crystal boundaries, absence of pinholes, lower defect density, and faster carrier mobility. Accordingly, the PSCs based on as-prepared CsPbI2Br film achieve a power conversion efficiency of 15.5% (the maximum stabilized power output of 15.02%). Moreover, the optimized CsPbI2Br films show excellent robustness against moisture and oxygen and maintain the photovoltaic dark phase after 3 h aging in an air atmosphere at room temperature and 35% relative humidity (R.H.). In comparison, the pristine films are completely converted to the yellow phase in 1.5 h.
Highlights
Since 2009, tremendous progress has been made in the power conversion efficiencies (PCEs) of organic–inorganic hybrid perovskite solar cells (PSCs), which have increased from 3.8 to 25.5% [1,2,3,4,5,6,7,8,9,10]
We systematically explored the effects of spin-coating temperature on the structure of CsPbI2 Br films
Air temperature assisted crystallization obviously improves the crystallized quality of perovskites along the (110) and (220) planes in this case. (ii) The crystallite size is inversely proportional to the FWHM of the diffraction peak according to the Scherrer formula in X-ray physics as follows [31]: Kλ βcosθ where D is the particle size in Å, K is the shape factor '0.9, λ is the wavelength (1.5418 Å, CuKα), β is the full width at half maximum (FWHM) of the peak, and θ is the peak position
Summary
Since 2009, tremendous progress has been made in the power conversion efficiencies (PCEs) of organic–inorganic hybrid perovskite solar cells (PSCs), which have increased from 3.8 to 25.5% [1,2,3,4,5,6,7,8,9,10]. Inorganic cesium lead halide perovskites (CsPbX3 , X = Cl, Br, I) have attracted considerable attention due to their high-temperature stability, where a stable phase can be retained even at temperatures exceeding 400 ◦ C [13,14,15]. Replacing the organic component with an inorganic component is widely regarded as the ultimate solution for addressing the thermal instability issue. CsPbI2 Br is a novel inorganic halide perovskite with a mid-range bandgap (1.92 eV), and it can operate even in the ambient atmosphere [20]. The efficiencies of CsPbI2 Br solar cells achieved to date are still low, principally as the result of poor CsPbI2 Br film quality, which
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